diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index aca70bc1239..133507483a6 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -438,6 +438,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
   template<typename _Tp, typename _Ref, typename _Ptr>
     struct _Deque_iterator;
 
+  struct _Bit_iterator;
+
 _GLIBCXX_END_NAMESPACE_CONTAINER
 
   // Helpers for streambuf iterators (either istream or ostream).
@@ -957,6 +959,10 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
 	      const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&,
 	      const _VTp&);
 
+  void
+  __fill_a1(_GLIBCXX_STD_C::_Bit_iterator, _GLIBCXX_STD_C::_Bit_iterator,
+	    const bool&);
+
   template<typename _FIte, typename _Tp>
     _GLIBCXX20_CONSTEXPR
     inline void
diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index f245e52b25d..a365e7182eb 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -416,39 +416,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     { return __x + __n; }
   };
 
-  inline void
-  __fill_bvector(_Bit_type * __v,
-		 unsigned int __first, unsigned int __last, bool __x)
-  {
-    const _Bit_type __fmask = ~0ul << __first;
-    const _Bit_type __lmask = ~0ul >> (_S_word_bit - __last);
-    const _Bit_type __mask = __fmask & __lmask;
-
-    if (__x)
-      *__v |= __mask;
-    else
-      *__v &= ~__mask;
-  }
-
-  inline void
-  fill(_Bit_iterator __first, _Bit_iterator __last, const bool& __x)
-  {
-    if (__first._M_p != __last._M_p)
-      {
-	_Bit_type* __first_p = __first._M_p;
-	if (__first._M_offset != 0)
-	  __fill_bvector(__first_p++, __first._M_offset, _S_word_bit, __x);
-
-	__builtin_memset(__first_p, __x ? ~0 : 0,
-			 (__last._M_p - __first_p) * sizeof(_Bit_type));
-
-	if (__last._M_offset != 0)
-	  __fill_bvector(__last._M_p, 0, __last._M_offset, __x);
-      }
-    else if (__first._M_offset != __last._M_offset)
-      __fill_bvector(__first._M_p, __first._M_offset, __last._M_offset, __x);
-  }
-
   template<typename _Alloc>
     struct _Bvector_base
     {
@@ -1336,15 +1303,46 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
   };
 
 _GLIBCXX_END_NAMESPACE_CONTAINER
-_GLIBCXX_END_NAMESPACE_VERSION
-} // namespace std
 
-#if __cplusplus >= 201103L
+  inline void
+  __fill_bvector(_GLIBCXX_STD_C::_Bit_type * __v,
+		 unsigned int __first, unsigned int __last, bool __x)
+  {
+    using _GLIBCXX_STD_C::_Bit_type;
+    using _GLIBCXX_STD_C::_S_word_bit;
+    const _Bit_type __fmask = ~0ul << __first;
+    const _Bit_type __lmask = ~0ul >> (_S_word_bit - __last);
+    const _Bit_type __mask = __fmask & __lmask;
 
-namespace std _GLIBCXX_VISIBILITY(default)
-{
-_GLIBCXX_BEGIN_NAMESPACE_VERSION
+    if (__x)
+      *__v |= __mask;
+    else
+      *__v &= ~__mask;
+  }
 
+  inline void
+  __fill_a1(_GLIBCXX_STD_C::_Bit_iterator __first,
+	    _GLIBCXX_STD_C::_Bit_iterator __last, const bool& __x)
+  {
+    using _GLIBCXX_STD_C::_Bit_type;
+    using _GLIBCXX_STD_C::_S_word_bit;
+    if (__first._M_p != __last._M_p)
+      {
+	_Bit_type* __first_p = __first._M_p;
+	if (__first._M_offset != 0)
+	  __fill_bvector(__first_p++, __first._M_offset, _S_word_bit, __x);
+
+	__builtin_memset(__first_p, __x ? ~0 : 0,
+			 (__last._M_p - __first_p) * sizeof(_Bit_type));
+
+	if (__last._M_offset != 0)
+	  __fill_bvector(__last._M_p, 0, __last._M_offset, __x);
+      }
+    else if (__first._M_offset != __last._M_offset)
+      __fill_bvector(__first._M_p, __first._M_offset, __last._M_offset, __x);
+  }
+
+#if __cplusplus >= 201103L
   // DR 1182.
   /// std::hash specialization for vector<bool>.
   template<typename _Alloc>
@@ -1354,10 +1352,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       size_t
       operator()(const _GLIBCXX_STD_C::vector<bool, _Alloc>&) const noexcept;
     };
+#endif // C++11
 
 _GLIBCXX_END_NAMESPACE_VERSION
-}// namespace std
-
-#endif // C++11
+} // namespace std
 
 #endif
diff --git a/libstdc++-v3/testsuite/25_algorithms/fill/bvector/1.cc b/libstdc++-v3/testsuite/25_algorithms/fill/bvector/1.cc
new file mode 100644
index 00000000000..22e4fca73b8
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/fill/bvector/1.cc
@@ -0,0 +1,39 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <algorithm>
+#include <vector>
+
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  using namespace std;
+
+  vector<bool> v1(100, false);
+  vector<bool> v2(100, true);
+
+  fill(v1.begin(), v1.end(), true);
+
+  VERIFY( equal(v1.begin(), v1.end(), v2.begin()) );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}